#define _CRT_SECURE_NO_WARNINGS 1
class Solution {
public:
    vector<int> seq;

    bool verifySequenceOfBST(vector<int> sequence) {
        seq = sequence;
        return dfs(0, seq.size() - 1);
    }
    bool dfs(int l, int r) {
        if (l >= r)  return true;
        int root = seq[r];
        int k = l;
        while (k < r && seq[k] < root) k++;
        for (int i = k; i < r; i++) {
            if (seq[i] < root)
                return false;
        }
        return dfs(l, k - 1) && dfs(k, r - 1);
    }
};
